Answer
The element is copper Cu.
Work Step by Step
The atomic mass of the element is found by multiplying each isotopic mass by its fraction, and then add all of them.
62.930 amu x 0.6909 = 43.478 amu
64.928 amu x 0.3091 = 20.069 amu
____________________________
Sum: 63.548 amu
We see in the periodic table of elements that copper Cu, has the atomic mass 63.546 amu, that is close to the number we found ( within experimental error).
Therefore the element is Cu.
